This paper experimentally observes the Normal Raman spectrum (NRS) and infrared absorption spectrum of methyl orange (MO) and presents theoretical vibrational spectra calculated from a density functional theory (DFT) method on the basis of B3LYP with 6–31 basis set. The calculated results show very good agreement with the experimentally observed IR and Raman frequencies. We also report the surface enhanced Raman spectrum (SERS) of MO adsorbed on silver nanoparticles surface. Finally, the possible adsorbed state of MO on the silver nanoparticles surface is discussed.